There’s something gut-wrenchingly effective about a child-in-peril movie, whether it’s played for laughs – think Home Alone – or with deadly seriousness, as in Denis Villeneuve’s Prisoners. But if that nail-biting tension is too much, be warned: Capernaum will have you chewing your fingers off.

Let’s start with Zain (Zain Al Rafeea), a 12-year-old growing up in the slums of Beirut. I say 12, but his age is a little uncertain; even his parents didn’t keep close track, and the movie isn’t clear about how many siblings he has, but it’s a lot. He’s closest to his little sister Sahar, until she’s sold into marriage and taken away. She’s 11.

Wait, did you think Zain was the child in peril here? I suppose he is, but his plight is nothing to that of Yonas, a toddler and the son of illegal immigrant Rahil (Yordanos Shiferaw). After Zain runs away from home, he is taken in by the Ethiopian woman, and winds up providing babysitting services in exchange for room and board.

When Rahil is caught up in a raid, Zain struggles to find enough money to feed himself and the baby, which is where the real peril sets in. There’s a shot of the older kid pulling the younger in a makeshift pram made from a pilfered skateboard and a cooking pot, with vehicular traffic whizzing by inches away from them. It’s terrifying.

Capernaum – the unfortunately obscure title means a confused jumble – is the latest from writer/director Nadine Labaki, whose 2011 film Where Do We Go Now? won the People’s Choice award at the Toronto Film Festival. This one doesn’t quite fit the definition of a crowd-pleaser, but it did win both the Jury Prize and the prize of the ecumenical jury at Cannes last May.

It’s a remarkably humanist story, although the set-up is a bit of a bait-and-switch. Trailers suggest this is the tale of Zain suing his parents, and indeed an early scene in the film has him declaring the reason for his legal action: “Because I was born.” It’s basically a citizen’s arrest for failing to provide the necessities of life.

But the movie is less a courtroom drama than an examination of the plight of the world’s underclass. Labaki drew many of the story’s elements from real life, including her pint-sized star; the real Zain is a Syrian refugee who had never acted before, and now lives in Norway. So presumably his anger and rough speech comes from a real place, but that doesn’t make the performance any less amazing.

And while Zain shows remarkable street smarts, he is also clearly still a child, with a limited knowledge of how the larger world works. One scene finds him practicing a story about why his “brother” Yonas is several shades darker than he is; he’ll say his mother drank coffee while she was pregnant, or that all her kids start out black and then get lighter over time.

Labaki works hard to keep us in Zain’s world, often by putting her camera near the ground so we perceive things from his level. That only ups the trepidation quotient, and the knowledge that, while the real Zain managed to escape his condition, there are thousands more like him, plying the streets of Beirut and other cities, an inch away from disaster.